A vehicle seat comprising: a pair of side frames which constitute left and right portions of a seat back frame; a projecting portion (force-receiving member) provided on an upper portion of an outer surface of a laterally outside side frame; and a diagonal brace disposed to extend diagonally from an upper portion of an inner surface of the laterally outside side frame to a lower portion of the inner surface of an opposite side frame to join the side frames has hitherto been known in the art (see JP 2007-326441 A).
In the vehicle seat as mentioned above, a side collision load imposed to the projecting portion from outside in a lateral direction is transmitted to a side opposite to that on which the projecting portion is provided, through the laterally outside side frame, the diagonal brace and the laterally inside side frame.
However, with the conventional technique, the diagonal brace disposed to extend diagonally from an upper portion of an inner surface of one side frame to a lower portion of an inner surface of the other side frame, and joined to these side frames; therefore, disadvantageously, rearward movement of an occupant which would be caused upon receipt of a side collision load is restricted.
Against this backdrop, the inventors named in the present application have created the present invention in the process of research for providing a vehicle seat in which occupant's rearward movement upon receipt of a rear-end collision load is permitted while the transmission of the side collision load can be achieved satisfactorily.